This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Defective antibody formation is the most common abnormality in the majority of primary immunodeficiency (PID) diseases. It is most often reflected by a decrease in serum immunoglobulins, which in turn leads to increased susceptibility to bacterial infections especially of the sinopulmonary tract. Individuals with these diseases require replacement therapy with immune globulins to prevent or reduce the severity of infections. For many years, immune globulin replacement therapy was given by the muscular and then by the intravenous (IV) route. Currently, the vast majority of immune globulins in the United States are licensed for IV administration. During the last few years, subcutaneous (SC) application of immune globulin preparations was introduced in many countries worldwide. This method of IgG replacement therapy is considered to be effective, safe and also highly appreciated by the patients as it has a low risk of adverse reactions and leads to higher trough serum IgG concentrations compared to monthly IV infusions. The purpose of the study is to evaluate the tolerability of IGIV, 10% given subcutaneously and the pharmacokinetics of immunoglobulin G (IgG) following subcutaneous (SC) treatment with IGIV, 10% in subjects with primary immunodeficiency (PID) disorders. Approximately 23 subjects with PID aged 12 years and older who had previously been treated with intravenous (IV) immunoglobulins and approximately 12 subjects with PID aged 2 to <12 years who also had received previous treatment with IV immunoglobulins will be enrolled and treated. The study will help assess the safety and efficacy of this mode of treatment.